1. Field of the Invention
The present invention relates to an X-ray CT (computer tomography) apparatus, and particularly, to an X-ray CT apparatus which has a real time CT value monitoring function, and is adapted to perform a monitoring of a CT value of a region of interest by a first scan and, when the CT value meets a predetermined condition, to execute a second scan for acquiring a clinical application image.
2. Description of Related Art
In a recent X-ray CT apparatus, with advancements for the detector to have higher performances and for the operational processor to have higher speeds, there has been achieved a real time reconstruction in which, while a scan is advancing, an image reconstruction is performed for display.
In a system, a technique for the real time reconstruction is applied to an X-ray CT radiography using contrast media, for monitoring a real time CT value. The system performs a first scan after injection of contrast media, monitoring a CT value of a region of interest, and performs a second scan when the state of distribution of the contrast media is optimized, acquiring an adequately media-contrasted image.
In the real time CT value monitoring system, a CT value of the region of interest is monitored in real time, and the image of an optimal state of distribution of contrast media is acquired in the second scan. Therefore, it is allowed for the contrast media to be decreased in quantity in use to reduce a burden on a patient, as well as for the number of scan times to be decreased to reduce the radiation exposure.
In an X-ray CT apparatus provided with such a system, a single region of interest is designated in a first scan and employed as an object of real time CT value monitoring.
Accordingly, the timing for a second scan to be executed is based on a decision on a CT value of the single region of interest, and the CT value needs to be always grasped at a high accuracy.
As a result, when subjected to a disturbance due such as to a movement of a patient, for example, the CT apparatus may have a different decision. As a countermeasure, the region of interest may be set at a point small of influences of such disturbances, or the apparatus is to cope with in a direction to discern a substance of the disturbance, having an exponentially increased quantity of computer resources allotted thereto, with an extended apprehension that the region of interest may be designated under restricted conditions.